Learnng to Draw: Getting to the Next Drawing

This one I invented before I drew it. A bike trip for groceries. I'd buy cabbage and speak to someone. Later from my position east or west--I hadn't decided yet--of the Safeway parking lot on 13th, the conversation would lend emotional weight to this drawing that all other drawings so far lacked.
I couldn't see how the drawing would work but there I was, helmet and grocery list in hand. And my drawing kit consisting of the Pentel P209 and the 5x8 sketchbook I bought from the Art Store on campus and started using, as a notebook, on April 11, 2012. I pedalled west on13th.
I couldn't find celery seed  but picked up a cabbage, forgetting to speak, and carried myself out the door to a perch half-way up the sidewalk of the acupuncture shack across the street. I drew a van the three of the 5 elms along the Safeway lot on the Retallack side, east. The left-hand tree seemed to penetrate the van, which soon drove off. I drew shadow, grateful for its uniform shade.
Should there be dialogue between an object (/subject) and its shadow? Mine was disappointing, a shortage of definition in all things, except the ones I didn't draw.